CN115021361A - Equalizing method for ternary lithium-lithium iron phosphate hybrid battery pack - Google Patents
Equalizing method for ternary lithium-lithium iron phosphate hybrid battery pack Download PDFInfo
- Publication number
- CN115021361A CN115021361A CN202210718563.9A CN202210718563A CN115021361A CN 115021361 A CN115021361 A CN 115021361A CN 202210718563 A CN202210718563 A CN 202210718563A CN 115021361 A CN115021361 A CN 115021361A
- Authority
- CN
- China
- Prior art keywords
- charging
- battery
- electric quantity
- battery pack
- iron phosphate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 238000000034 method Methods 0.000 title claims abstract description 54
- NCZYUKGXRHBAHE-UHFFFAOYSA-K [Li+].P(=O)([O-])([O-])[O-].[Fe+2].[Li+] Chemical compound [Li+].P(=O)([O-])([O-])[O-].[Fe+2].[Li+] NCZYUKGXRHBAHE-UHFFFAOYSA-K 0.000 title claims abstract description 41
- 238000007600 charging Methods 0.000 claims abstract description 146
- 239000000178 monomer Substances 0.000 claims abstract description 51
- 230000003247 decreasing effect Effects 0.000 claims abstract description 3
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 claims description 40
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 36
- 229910052744 lithium Inorganic materials 0.000 claims description 36
- 238000005070 sampling Methods 0.000 claims description 17
- 230000032683 aging Effects 0.000 claims description 4
- 230000005611 electricity Effects 0.000 claims description 4
- 230000010354 integration Effects 0.000 claims description 4
- 230000002265 prevention Effects 0.000 claims description 3
- 238000012804 iterative process Methods 0.000 claims description 2
- 238000010586 diagram Methods 0.000 description 7
- 230000000694 effects Effects 0.000 description 4
- 230000002238 attenuated effect Effects 0.000 description 2
- 238000010277 constant-current charging Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000003892 spreading Methods 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0013—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries acting upon several batteries simultaneously or sequentially
- H02J7/0014—Circuits for equalisation of charge between batteries
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/007—Regulation of charging or discharging current or voltage
- H02J7/00712—Regulation of charging or discharging current or voltage the cycle being controlled or terminated in response to electric parameters
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/70—Energy storage systems for electromobility, e.g. batteries
Abstract
The invention discloses a balancing method of a ternary lithium-lithium iron phosphate mixed battery pack, which comprises the following steps: step 1, setting voltage threshold values for batteries of two systems; step 2, when the sum of the charging voltages of the single batteries is respectively greater than or equal to the voltage threshold of each system, calculating the charging current integral of the single batteries until the charging is finished, and obtaining the charging electric quantity corresponding to each single battery; step 3, selecting the monomer with the minimum charging capacity in the battery respectively, differentiating the corresponding charging capacities to obtain the charging capacity difference of the special-shaped battery core, and performing charging capacity difference iteration to obtain an iteration result; step 4, taking an iteration result as a target balanced discharge electric quantity; step 5, feeding back the estimation of the charging electric quantity difference of the special-shaped battery cell, and judging whether the charging electric quantity difference is increased or decreased due to natural evolution of the special-shaped battery cell; step 6, performing difference iteration on the target balanced discharge electric quantity and the discharge balanced electric quantity; and 7, judging whether the battery pack performs special-shaped battery cell balancing operation or not according to the comparison between the difference value and the set value.
Description
Technical Field
The invention relates to the technical field of battery management systems, in particular to a balancing method of a ternary lithium-lithium iron phosphate hybrid battery pack.
Background
The method can be used in echelon, has higher sustainability and can be further widely applied to electric vehicles and power grid energy storage for manufacturing the lithium iron phosphate core with lower carbon emission. However, compared with a ternary lithium battery, the lithium iron phosphate battery still has the defects of energy density, low-temperature performance and the like, and the current battery pack is composed of a single battery cell and cannot give full play to the advantages of batteries of various systems. However, under reasonable configuration matching and management, the ternary lithium-lithium iron phosphate hybrid battery pack can effectively reduce the risk of heat spreading, harmonize the cost and the energy density, and comprehensively exert the respective advantages of two battery cells, so that the ternary lithium-lithium iron phosphate hybrid battery pack is expected to replace two pure battery packs.
However, it should be noted that the self-discharge rate and the aging rate of the two different systems of single batteries are different from each other, and if no corresponding correction measure is taken, the configuration of the hybrid battery pack is changed due to the electric quantity difference between the special-shaped battery cells in the long-term use process of the hybrid battery pack, so that the available energy of the hybrid battery pack is attenuated, and the user experience is seriously affected.
Therefore, the abnormal-shaped difference state observer is provided for the abnormal-shaped cell difference, the charging electric quantity difference of the abnormal-shaped cell of the hybrid battery pack is fed back intermittently in a long period, and the stable or less-attenuation energy output expectation is realized by combining the capacity and electric quantity matching of the equalization algorithm adjusting configuration.
Disclosure of Invention
The present invention is made to solve the above problems, and an object of the present invention is to provide an equalization method for a ternary lithium-lithium iron phosphate hybrid battery pack.
The invention provides a balancing method of a ternary lithium-lithium iron phosphate hybrid battery pack, which is characterized in that the hybrid battery pack comprises N ternary lithium battery monomers and N lithium iron phosphate battery monomers, wherein the ternary lithium battery monomers and the lithium iron phosphate battery monomers are connected in series, and the balancing method comprises the following steps: step 1, respectively setting voltage threshold values U for batteries of two systems in the charging process T_NCM And U T_LFP (ii) a Step 2, charging voltage U of each single battery of the two-system battery NCM，i And U LFP，i Are respectively greater than or equal to the voltage threshold U of each system T_NCM And U T_LFP At the beginning ofCalculating the charging current integral of the single bodies until the charging is finished to obtain the charging electric quantity Q corresponding to each battery single body of the two systems at the moment NCM，i And Q LFP，i (ii) a Step 3, respectively selecting the monomer with the minimum charging electric quantity in the two systems of batteries to ensure that the corresponding charging electric quantity Q is the charging electric quantity NCM，i And Q LFP，i Obtaining the difference Q of the charging electric quantity of the special-shaped battery core D Taking the obtained current as a control target for balancing the special-shaped electric core of the hybrid battery pack, and performing charging electric quantity difference iteration when the next charging is finished to obtain an iteration result; step 4, taking the iteration result as a target balanced discharge electric quantity Q E (ii) a Step 5, feeding back the charging capacity difference Q of the special-shaped battery cell according to the special-shaped difference state observer D The estimation of (2) judging whether the abnormal-shaped battery cell has the charging capacity difference Q caused by natural evolution D Increase or decrease; step 6, equalizing the target discharge electric quantity Q E Performing difference iteration with the discharge balance electric quantity of the balance resistor of the corresponding battery system in each sampling period delta t; step 7, according to the difference value and the set value Q d And (4) comparing, judging whether the hybrid battery pack performs special-shaped battery cell balancing operation or not, and controlling the balancing controller to be opened or closed.
The balancing method of the ternary lithium-lithium iron phosphate mixed battery pack provided by the invention can also have the following characteristics that: wherein, in step 1, setting a voltage threshold U T_NCM And U T_LFP In the process, because the upper and lower limit cut-off voltage ranges of the battery monomers of the two systems are different, the charging voltage of each system of the battery monomers needs to be monitored respectively, so that the ternary lithium battery and the lithium iron phosphate battery respectively select partial charging voltage curves, and the set standard of the lithium iron phosphate battery system is behind the plateau period.
The balancing method of the ternary lithium-lithium iron phosphate mixed battery pack provided by the invention can also have the following characteristics that: wherein, in step 2, the charge capacity Q is estimated by current integration NCM，i And Q LFP，i (ii) a If the ternary lithium monomer in the hybrid battery pack reaches the threshold value when the charging of the battery pack is finished, the three-dimensional lithium monomer is represented as:
if the lithium iron phosphate monomer in the hybrid battery pack reaches the threshold value when the charging of the battery pack is finished, the method is represented as follows:
wherein I is the battery charging current, t e End of charge time, t, for a hybrid battery N，s 、t L，s Respectively corresponding to the voltage thresholds of ternary lithium and lithium iron phosphate NCM，i Charging capacity for ith ternary lithium monomer, Q LFP，i And charging the electricity quantity for the ith lithium iron phosphate monomer.
The balancing method of the ternary lithium-lithium iron phosphate mixed battery pack provided by the invention can also have the following characteristics that: in step 3, the balancing types of the hybrid battery pack include homogeneous cell balancing and heterogeneous cell balancing.
The balancing method of the ternary lithium-lithium iron phosphate mixed battery pack provided by the invention can also have the following characteristics that: and for the same-type battery cell equalization, the equalization channel is controlled by adopting an equalization algorithm with consistent residual charging capacity.
The balancing method of the ternary lithium-lithium iron phosphate mixed battery pack provided by the invention can also have the following characteristics that: wherein, for the balance of the special-shaped battery core, the control process is as follows: respectively selecting the monomer with the minimum charging electric quantity in the two systems of batteries to ensure that the corresponding charging electric quantity Q is NCM，i And Q LFP，i By difference, the values are expressed as:
Q D ＝min(Q LFP，i )-min(Q NCM，i )
in the formula, min (Q) LFP，i ) Is a lithium iron phosphate monomer with the minimum charging capacity in the mixed battery pack, min (Q) NCM，i ) Is a ternary lithium monomer, Q, with the least amount of charge in the hybrid battery pack D The difference of the charging electric quantity of the special-shaped battery core.
The balancing method of the ternary lithium-lithium iron phosphate mixed battery pack provided by the invention can also have the following characteristics that: the iterative process of the charging capacity difference of the special-shaped battery cell is represented as follows:
Q e ＝Q D，0 -Q D，i
in the formula, Q D，0 Is the initial charging capacity difference, Q, of the special-shaped electric core under the original configuration of the hybrid battery pack D，i Is the difference of the charging electric quantity recorded at the end of the ith charging between the special-shaped electric cores, Q e The theoretical target balance electric quantity of the special-shaped electric core is the target balance electric quantity Q, and in order to prevent the generation of over balance, an over balance prevention coefficient K is selected, wherein K is less than 1 E Comprises the following steps:
Q E ＝KQ e 。
the balancing method of the ternary lithium-lithium iron phosphate mixed battery pack provided by the invention can also have the following characteristics that: wherein, in step 5, the natural evolution becomes: in practical situations, because the electric quantity changes of each monomer in the series hybrid battery pack are not completely consistent, and the self-discharge rate, the aging rate and other characteristics of the ternary lithium battery system and the lithium iron phosphate battery system are different, the batteries of each system show different attenuation rates, so that the charging electric quantity difference Q between the special-shaped battery cells is caused D Increase or decrease.
The balancing method of the ternary lithium-lithium iron phosphate mixed battery pack provided by the invention can also have the following characteristics that: in step 5, judging whether the charging capacity difference Q of the special-shaped battery cell is caused by natural evolution or not D In the process of increasing or decreasing, cell attenuation caused by the self-discharge rate is mainly considered.
The balancing method of the ternary lithium-lithium iron phosphate mixed battery pack provided by the invention also has the following characteristics that: wherein, in step 6, the target balance discharge electric quantity Q E And the difference is made with the discharge balance electric quantity of the balance resistance of the corresponding battery system in each sampling period delta t, and the value is expressed as:
Q E，i+1 ＝Q E，i -I E ·Δt
in the formula, Q E，i Is between special-shaped electric cores in the battery packTarget equalization of electrical quantities in the ith sampling period, I E Is a vector formed by the balance currents of each monomer, delta t is the duration of each sampling period, Q E，i+1 And the target balance electric quantity among the abnormal-shaped electric cores in the (i + 1) th sampling period is obtained.
Action and Effect of the invention
According to the balancing method of the ternary lithium-lithium iron phosphate mixed battery pack, the specific process is as follows: step 1, respectively setting voltage threshold values U for batteries of two systems in the charging process T_NCM And U T_LFP (ii) a Step 2, charging voltage U of each single battery of the two-system battery NCM，i And U LFP，i Are respectively greater than or equal to the voltage threshold U of each system T_NCM And U T_LFP Then, the charging current integral of the single battery starts to be calculated until the charging is finished, and the charging electric quantity Q corresponding to each battery single battery of the two systems is obtained NCM，i And Q LFP，i (ii) a Step 3, respectively selecting the monomer with the minimum charging electric quantity in the two systems of batteries to ensure that the corresponding charging electric quantity Q is the charging electric quantity NCM，i And Q LFP，i Obtaining the difference Q of the charging electric quantity of the special-shaped battery core D Taking the obtained current as a control target for balancing the special-shaped electric core of the hybrid battery pack, and performing charging electric quantity difference iteration when the next charging is finished to obtain an iteration result; step 4, taking the iteration result as a target balanced discharge electric quantity Q E (ii) a Step 5, feeding back the charging capacity difference Q of the special-shaped battery cell according to the special-shaped difference state observer D The estimation of (2) judging whether the abnormal-shaped battery cell has the charging capacity difference Q caused by natural evolution D Increase or decrease; step 6, equalizing the target discharge electric quantity Q E Performing difference iteration with the discharge balance electric quantity of the balance resistor of the corresponding battery system in each sampling period delta t; step 7, according to the difference value and the set value Q d And (4) comparing, judging whether the hybrid battery pack performs special-shaped battery cell balancing operation or not, and controlling the balancing controller to be opened or closed.
Therefore, on the basis of realizing the uniformity balance of the charging electric quantity of the same-type battery cells, the invention further provides the difference of the charging electric quantity of the special-shaped battery cells, and the difference is used as a control target for the balance of the special-shaped battery cells to judge the attenuation state of each system battery, so that the balance algorithm is adopted to ensure the stability of the difference of the charging electric quantity of the special-shaped battery cells.
Furthermore, the method and the device provided by the invention can dynamically adjust the available capacity and electric quantity intervals of different battery systems by intermittently feeding back the charging electric quantity difference of the special-shaped battery cell for a long period, thereby maintaining stable energy output of the hybrid battery pack under different attenuation degrees, fully utilizing the configuration advantages of the ternary lithium-lithium iron phosphate hybrid battery pack and obtaining excellent user experience.
Drawings
Fig. 1 is a flowchart of an equalizing method of a ternary lithium-lithium iron phosphate hybrid battery pack according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a ternary lithium-lithium iron phosphate battery configuration in an embodiment of the present invention;
FIG. 3 is a schematic diagram of the integration of charging current for a ternary lithium battery system in an embodiment of the present invention;
FIG. 4 is a schematic of the charging current integral for a lithium iron phosphate battery system in an example of the invention;
fig. 5 is a schematic diagram of the balance correction of the special-shaped battery cells in the embodiment of the present invention.
Detailed Description
In order to make the technical means, creation features, achievement purposes and effects of the present invention easy to understand, the following embodiments specifically describe the balancing method of the ternary lithium-lithium iron phosphate hybrid battery pack according to the present invention with reference to the accompanying drawings.
In this embodiment, a balancing method for a ternary lithium-iron phosphate lithium hybrid battery pack is provided.
Fig. 1 is a flowchart of an equalizing method of a ternary lithium-lithium iron phosphate hybrid battery pack according to an embodiment of the present invention.
As shown in fig. 1, the hybrid battery pack includes N ternary lithium battery cells and N lithium iron phosphate battery cells, and the ternary lithium battery cells and the lithium iron phosphate battery cells are connected in series, and the battery pack includes 4 ternary lithium battery cells and 4 lithium iron phosphate battery cells in this embodiment. The balancing method of the ternary lithium-lithium iron phosphate hybrid battery pack related to the embodiment comprises the following steps:
step S1, setting voltage threshold U for two batteries respectively during charging T_NCM And U T_LFP 。
At a set voltage threshold U T_NCM And U T_LFP In the process, because the upper and lower limit cut-off voltage ranges of the battery cells of the two systems are different, the charging voltage of each system cell needs to be monitored respectively, so that the ternary lithium battery and the lithium iron phosphate battery respectively select partial charging voltage curves, the set standard of the lithium iron phosphate battery system is after the plateau phase, and in the embodiment, U is taken T_NCM 3.75V (volts) and U T_LFP 3.35V (volts).
Step S2, when each single charging voltage U of the two-system battery NCM，i And U LFP，i Are respectively greater than or equal to the voltage threshold U of each system T_NCM And U T_LFP Then, the charging current integral of the single battery starts to be calculated until the charging is finished, and the charging electric quantity Q corresponding to each battery single battery of the two systems is obtained NCM，i And Q LFP，i 。
Fig. 2 is a schematic diagram of a ternary lithium-lithium iron phosphate battery configuration in an embodiment of the invention.
Because the upper and lower limit cut-off voltage ranges of the two system battery monomers are different, the charging voltage of each system battery monomer needs to be monitored respectively. As shown in fig. 2, the charge/discharge cutoff states of the ternary lithium-iron phosphate lithium hybrid battery pack are respectively referred to as charge cutoff states S PN，F And discharge cutoff state S PL，E . In the original configuration of this example, the ternary lithium battery and the lithium iron phosphate battery control the emptying and full charge states of the battery pack, respectively.
However, in the practical use of the hybrid battery pack, the charging current is not always fixed and sometimes varies with the operating condition, so that the estimation of the charging capacity by integrating the current is more accurate.
Fig. 3 is a schematic diagram of charging current integration of a ternary lithium battery system in an embodiment of the present invention.
As shown in fig. 3, a constant current charging mode is adopted for a partial charging voltage curve of 4 ternary lithium monomers in the ternary lithium-iron phosphate lithium battery pack. If the battery pack is charged to the end, then the ternary lithium cell in the hybrid battery pack reaches the threshold value at the end of charging, which can be expressed as:
fig. 4 is a schematic diagram of the charging current integral of a lithium iron phosphate battery system in an example of the present invention.
As shown in fig. 4, a constant current charging mode is adopted for a partial charging voltage curve of 4 lithium iron phosphate monomers in the ternary lithium-iron phosphate lithium battery pack. If the charging of the battery pack is finished, the lithium iron phosphate monomer in the hybrid battery pack reaches the threshold value at the end of charging, which can be expressed as:
wherein I is the battery charging current, t e End of charge time, t, for a hybrid battery N，s 、 t L，s The time corresponding to the voltage threshold of ternary lithium and lithium iron phosphate respectively, Q NCM，i Charging capacity for ith ternary lithium monomer, Q LFP，i And charging the electricity quantity for the ith lithium iron phosphate monomer.
Step S3, selecting the monomer with the minimum charging quantity from the two system batteries respectively to make the charging quantity Q corresponding to the monomer NCM，i And Q LFP，i Obtaining the difference Q of the charging capacity of the special-shaped cell D And the current charging capacity difference is used as a control target for balancing the special-shaped electric core of the hybrid battery pack, and the charging capacity difference iteration is carried out when the next charging is finished, so that an iteration result is obtained.
In addition, the ternary lithium-lithium iron phosphate hybrid battery pack is divided into a homogeneous cell balance and a heterogeneous cell balance. And aiming at the equalization of the same type of battery cells, an equalization algorithm with consistent residual charging electric quantity is adopted to control the equalization channel. The embodiment mainly discusses the balance of the special-shaped battery cell, and specifically includes:
selecting the monomer with the minimum charge capacity in the two systems as a difference, wherein the value can be expressed as:
Q D ＝min(Q LFP，i )-min(Q NCM，i )
in the formula, min (Q) LFP，i ) Is a lithium iron phosphate monomer with the minimum charging capacity in the mixed battery pack, min (Q) NCM，i ) Is a ternary lithium monomer, Q, with the least amount of charge in the hybrid battery pack D The difference of the charging electric quantity of the special-shaped battery core.
The difference iteration of the charging electric quantity of the special-shaped battery core can be expressed as:
Q e ＝Q D，0 -Q D，i
in the formula, Q D，0 Is the initial charging capacity difference, Q, of the special-shaped electric core under the original configuration of the hybrid battery pack D，i Is the difference of the charging electric quantity recorded at the end of the ith charging between the special-shaped electric cores, Q e The method is a theoretical target balance electric quantity of the special-shaped battery cell.
In order to prevent the generation of the over-balance, an over-balance prevention coefficient K is selected, wherein K is less than 1, namely the target balance discharge electric quantity Q E Comprises the following steps:
Q E ＝KQ e 。
step S4, taking the iteration result as the target balance discharge electric quantity Q E 。
Step S5, feeding back the charging capacity difference Q of the special-shaped battery cell according to the special-shaped difference state observer D The estimation of (2) judging whether the abnormal-shaped battery cell has the charging capacity difference Q caused by natural evolution D Increase or decrease.
In practical situations, because the electric quantity changes of each monomer in the series hybrid battery pack are not completely consistent, and the self-discharge rate, the aging rate and other characteristics of the ternary lithium battery system and the lithium iron phosphate battery system are different, the batteries of each system show different attenuation rates, so that the charging electric quantity difference Q between the special-shaped battery cells is caused D Increase or decrease. In the present embodiment, cell attenuation caused by self-discharge is mainly considered.
Fig. 5 is a schematic diagram of the balance correction of the special-shaped battery cells in the embodiment of the present invention.
As shown in fig. 5, in the hybrid battery pack, if three-way lithium batteryWhen the system attenuation is larger than that of the lithium iron phosphate battery system, the discharge cut-off state S of the ternary lithium battery system PN，E Is upwardly offset compared to the original configuration; charge cut-off state S for lithium iron phosphate battery system PL，F The difference Q of the charging electric quantity among the special-shaped electric cores is caused by downward deviation compared with the original configuration D And (4) increasing. On the contrary, if the attenuation of the lithium iron phosphate battery system is larger than that of the ternary lithium battery system, the discharge cut-off state S of the ternary lithium battery system PN，E Shifted downward compared to the original configuration. Charge cut-off state S for lithium iron phosphate battery system PL，F Compared with the original configuration, the charging capacity difference Q between the special-shaped electric cores is caused by upward deviation D And (4) reducing. If not, the charge quantity difference Q is maintained stably D The output energy of the hybrid battery pack is reduced, and the mileage of the pure electric vehicle is greatly reduced.
Step S6, discharging electric quantity Q with target balance E And performing difference iteration with the discharge balance electric quantity of the balance resistor of the corresponding battery system in each sampling period delta t.
Wherein the target balance discharge electric quantity Q E And the difference is made with the discharge balance electric quantity of the balance resistance of the corresponding battery system in each sampling period delta t, and the value is expressed as:
Q E，i+1 ＝Q E，i -I E ·Δt
in the formula, Q E，i Is the target balance electric quantity in the ith sampling period among the special-shaped electric cores in the battery pack, I E Is a vector formed by the balance currents of each monomer, delta t is the duration of each sampling period, Q E，i+1 And the target balance electric quantity among the abnormal-shaped electric cores in the (i + 1) th sampling period is obtained.
Step S7, according to the difference and the set value Q d And (4) comparing, judging whether the hybrid battery pack performs special-shaped battery cell balancing operation or not, and controlling the balancing controller to be opened or closed. Value Q is set in the present embodiment d Is taken as 5mAh
According to the balancing method of the ternary lithium-lithium iron phosphate hybrid battery pack, after the hybrid battery pack is balanced by the special-shaped battery cells, the usable capacity and electric quantity interval of the special-shaped battery cell configuration is readjusted, and the electric quantity difference among the special-shaped battery cells is maintained, so that the energy output expectation of the hybrid battery pack is stably or less attenuated.
Effects and effects of the embodiments
According to the balancing method of the ternary lithium-iron phosphate mixed battery pack related to the embodiment, the specific process is as follows: step 1, respectively setting voltage threshold values U for batteries of two systems in the charging process T_NCM And U T_LFP (ii) a Step 2, charging voltage U of each single battery of the two-system battery NCM，i And U LFP，i Are respectively greater than or equal to the voltage threshold U of each system T_NCM And U T_LFP Then, the charging current integral of the single battery starts to be calculated until the charging is finished, and the charging electric quantity Q corresponding to each battery single battery of the two systems is obtained NCM，i And Q LFP，i (ii) a Step 3, respectively selecting the monomer with the minimum charging electric quantity in the two systems of batteries to ensure that the corresponding charging electric quantity Q is the charging electric quantity NCM，i And Q LFP，i Obtaining the difference Q of the charging electric quantity of the special-shaped battery core D Taking the obtained current as a control target for balancing the special-shaped electric core of the hybrid battery pack, and performing charging electric quantity difference iteration when the next charging is finished to obtain an iteration result; step 4, taking the iteration result as a target balanced discharge electric quantity Q E (ii) a Step 5, feeding back the charging capacity difference Q of the special-shaped battery cell according to the special-shaped difference state observer D The estimation of (2) judging whether the abnormal-shaped battery cell has the charging capacity difference Q caused by natural evolution D Increase or decrease; step 6, equalizing the target discharge electric quantity Q E Performing difference iteration with the discharge balance electric quantity of the balance resistor of the corresponding battery system in each sampling period delta t; step 7, according to the difference value and the set value Q d And (4) comparing, judging whether the hybrid battery pack performs special-shaped battery cell balancing operation or not, and controlling the balancing controller to be opened or closed.
Therefore, the embodiment further provides the difference of the charging electric quantity of the special-shaped battery cell on the basis of realizing the uniformity balance of the charging electric quantity of the same-type battery cell, and the difference is used as a control target for the balance of the special-shaped battery cell to judge the attenuation state of each system battery, so that the balance algorithm is adopted to ensure the stability of the difference of the charging electric quantity of the special-shaped battery cell.
Further, in the embodiment, the available capacity and electric quantity intervals of different battery systems are dynamically adjusted by intermittently feeding back the charging electric quantity difference of the special-shaped battery cell for a long period, so that stable energy output of the hybrid battery pack is maintained under different attenuation degrees, the configuration advantages of the ternary lithium-lithium iron phosphate hybrid battery pack are fully utilized, and excellent user experience is obtained.
The above embodiments are preferred examples of the present invention, and are not intended to limit the scope of the present invention.
Claims (10)
1. The method for balancing the ternary lithium-lithium iron phosphate hybrid battery pack is characterized in that the hybrid battery pack comprises N ternary lithium battery monomers and N lithium iron phosphate battery monomers, wherein the ternary lithium battery monomers and the lithium iron phosphate battery monomers are connected in series, and the method comprises the following steps of:
step 1, respectively setting voltage threshold values U for batteries of two systems in the charging process T_NCM And U T_LFP ；
Step 2, charging voltage U of each single battery of the two-system battery NCM，i And U LFP，i Are respectively greater than or equal to the voltage threshold U of each system T_NCM And U T_LFP Then, the charging current integral of the single battery starts to be calculated until the charging is finished, and the charging electric quantity Q corresponding to each battery single battery of the two systems is obtained NCM，i And Q LFP，i ；
Step 3, respectively selecting the monomer with the minimum charging electric quantity in the two systems of batteries to ensure that the corresponding charging electric quantity Q is the charging electric quantity NCM，i And Q LFP，i Obtaining the difference Q of the charging electric quantity of the special-shaped battery core D Taking the obtained current as a control target for balancing the special-shaped electric core of the hybrid battery pack, and performing charging electric quantity difference iteration when the next charging is finished to obtain an iteration result;
step 4, taking the iteration result as a target balance discharge electric quantity Q E ；
Step 5, feeding back the special-shaped battery cell charging electricity according to the special-shaped difference state observerDifference in amount Q D The estimation of (2) judging whether the abnormal-shaped battery cell has the charging capacity difference Q caused by natural evolution D Increase or decrease;
step 6, equalizing the target discharge electric quantity Q E Performing difference iteration with the discharge balance electric quantity of the balance resistor of the corresponding battery system in each sampling period delta t;
step 7, according to the difference value and a set value Q d And (4) comparing, judging whether the hybrid battery pack performs special-shaped battery cell balancing operation or not, and controlling the balancing controller to be opened or closed.
2. The balancing method for the ternary lithium-lithium iron phosphate hybrid battery pack according to claim 1, characterized in that:
wherein, in step 1, the voltage threshold U is set T_NCM And U T_LFP In the process, because the upper and lower limit cut-off voltage ranges of the battery monomers of the two systems are different, the charging voltage of each system of the battery monomers needs to be monitored respectively, so that the ternary lithium battery and the lithium iron phosphate battery respectively select partial charging voltage curves, and the set standard of the lithium iron phosphate battery system is behind the plateau period.
3. The balancing method for the ternary lithium-lithium iron phosphate hybrid battery pack according to claim 1, characterized in that:
wherein in step 2, the charge quantity Q is estimated by current integration NCM，i And Q LFP，i ：
If the ternary lithium monomer in the hybrid battery pack reaches the threshold value when the charging of the battery pack is finished, the three-dimensional lithium monomer is represented as:
if the lithium iron phosphate monomer in the hybrid battery pack reaches the threshold value when the charging of the battery pack is finished, the method is represented as follows:
wherein I is the battery charging current, t e End of charge time, t, for a hybrid battery N，s 、t L，s Respectively corresponding to the voltage thresholds of ternary lithium and lithium iron phosphate NCM，i Charging capacity for ith ternary lithium monomer, Q LFP，i And charging the electricity quantity for the ith lithium iron phosphate monomer.
4. The balancing method for the ternary lithium-lithium iron phosphate hybrid battery pack according to claim 1, characterized in that:
in step 3, the balancing types of the hybrid battery pack include homogeneous cell balancing and heterogeneous cell balancing.
5. The balancing method of the ternary lithium-lithium iron phosphate hybrid battery pack according to claim 4, characterized in that:
and for the same type of battery cell equalization, performing equalization channel control by adopting an equalization algorithm with consistent residual charge capacity.
6. The balancing method of the ternary lithium-lithium iron phosphate hybrid battery pack according to claim 4, characterized in that:
for the balance of the special-shaped battery cell, the control process is as follows:
respectively selecting the monomer with the minimum charging electric quantity in the two systems of batteries to ensure that the corresponding charging electric quantity Q is NCM，i And Q LFP，i By difference, the values are expressed as:
Q D ＝min(Q LFP，i )-min(Q NCM，i )
in the formula, min (Q) LFP，i ) Is a lithium iron phosphate monomer with the minimum charging capacity in the mixed battery pack, min (Q) NCM，i ) Is a ternary lithium monomer, Q, with the least amount of charge in the hybrid battery pack D The difference of the charging electric quantity of the special-shaped battery core.
7. The balancing method for the ternary lithium-lithium iron phosphate hybrid battery pack according to claim 1, characterized in that:
wherein the iterative process of the charging capacity difference of the heterotype electric core is represented as:
Q e ＝Q D，0 -Q D，i
in the formula, Q D，0 Is the initial charging capacity difference, Q, of the special-shaped electric core under the original configuration of the hybrid battery pack D，i Is the difference of the charging electric quantity recorded at the end of the ith charging between the special-shaped electric cores, Q e Is the theoretical target balance electric quantity of the special-shaped electric core,
in order to prevent the generation of the over-balance, an over-balance prevention coefficient K is selected, wherein K is less than 1, namely the target balance discharge electric quantity Q E Comprises the following steps:
Q E ＝KQ e 。
8. the balancing method for the ternary lithium-lithium iron phosphate hybrid battery pack according to claim 1, characterized in that:
wherein, in step 5, the natural evolution becomes:
in practical situations, because the electric quantity changes of each monomer in the series hybrid battery pack are not completely consistent, and the characteristics of the self-discharge rate, the aging rate and the like of the ternary lithium battery system and the lithium iron phosphate battery system are different, the batteries of each system present different attenuation rates, so that the charging electric quantity difference Q between the special-shaped battery cores is caused D Increase or decrease.
9. The balancing method for the ternary lithium-iron phosphate mixed battery pack according to claim 1 or 8, characterized in that:
in step 5, it is determined whether the charging capacity difference Q of the special-shaped battery cell is caused by natural evolution D In the process of increasing or decreasing, cell attenuation caused by the self-discharge rate is mainly considered.
10. The balancing method for the ternary lithium-lithium iron phosphate hybrid battery pack according to claim 1, characterized in that:
wherein, in step 6, the target balance dischargeQuantity Q E And the difference is made with the discharge balance electric quantity of the balance resistance of the corresponding battery system in each sampling period delta t, and the value is expressed as:
Q E，i+1 ＝Q E，i -I E ·Δt
in the formula, Q E，i Is the target balance electric quantity in the ith sampling period among the special-shaped electric cores in the battery pack, I E Is a vector formed by the balance currents of each monomer, delta t is the duration of each sampling period, Q E，i+1 And the target balance electric quantity among the abnormal-shaped electric cores in the (i + 1) th sampling period is obtained.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210718563.9A CN115021361A (en) | 2022-06-23 | 2022-06-23 | Equalizing method for ternary lithium-lithium iron phosphate hybrid battery pack |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210718563.9A CN115021361A (en) | 2022-06-23 | 2022-06-23 | Equalizing method for ternary lithium-lithium iron phosphate hybrid battery pack |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN115021361A true CN115021361A (en) | 2022-09-06 |
Family
ID=83077335
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202210718563.9A Pending CN115021361A (en) | 2022-06-23 | 2022-06-23 | Equalizing method for ternary lithium-lithium iron phosphate hybrid battery pack |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN115021361A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116073492A (en) * | 2023-04-04 | 2023-05-05 | 江苏纳通能源技术有限公司 | Passive balance control method between battery cells |
| CN117214726A (en) * | 2023-11-02 | 2023-12-12 | 江苏天合储能有限公司 | State detection method and device, electronic equipment and computer readable storage medium |
-
2022
- 2022-06-23 CN CN202210718563.9A patent/CN115021361A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116073492A (en) * | 2023-04-04 | 2023-05-05 | 江苏纳通能源技术有限公司 | Passive balance control method between battery cells |
| CN117214726A (en) * | 2023-11-02 | 2023-12-12 | 江苏天合储能有限公司 | State detection method and device, electronic equipment and computer readable storage medium |
| CN117214726B (en) * | 2023-11-02 | 2024-01-26 | 江苏天合储能有限公司 | State detection method and device, electronic equipment and computer readable storage medium |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN106340926B (en) | Lithium battery Balance route policy optimization method | |
| CN115021361A (en) | Equalizing method for ternary lithium-lithium iron phosphate hybrid battery pack | |
| CN110429693B (en) | Energy storage battery pack power control method based on battery pack consistency | |
| US7940027B2 (en) | Battery and methods with real time charge and discharge management | |
| CN110635187B (en) | Lithium battery charging method considering aging | |
| CN109633460A (en) | A kind of general battery charge state capacity estimation method | |
| CN112060982B (en) | Dynamically balanced fuel cell unmanned aerial vehicle energy management method | |
| US8354824B2 (en) | System and method for charging and discharging a Li-ion battery pack | |
| CN105742738A (en) | Method for increasing low-temperature discharge capacity by adjusting discharge cut-off voltage of battery | |
| US20170338667A1 (en) | Model-based fast-charging method based on lithium surface concentration | |
| KR20160051571A (en) | Method and apparatus for fast charging of battery | |
| WO2019184849A1 (en) | Automobile, power battery pack equalization method and device | |
| CN105634063A (en) | Battery historical data based active equalization method | |
| CN111090963A (en) | Self-adaptive multi-section constant-current constant-voltage charging method based on user requirements | |
| CN112816893B (en) | Method for rapidly estimating capacity of battery pack based on residual charging capacity of battery pack monomer | |
| KR102086631B1 (en) | Charging Method of Secondary Battery and Charging Apparatus of the Same | |
| Lv et al. | Influence of equalization on LiFePO4 battery inconsistency | |
| CN111668894A (en) | Lithium battery pack rapid charging control method based on charging and equalization combination optimization | |
| CN107369858A (en) | A kind of battery pack Bi-objective equalizing circuit control strategy stage by stage | |
| CN112054571B (en) | Lithium battery energy storage system SOC consistency balancing method | |
| CN113602148B (en) | Balanced duration management method for full-time balancing | |
| CN111082174B (en) | Three-section type charging method for lithium ion battery | |
| CN113013938B (en) | Multi-branch parallel-connection grid-connected battery energy storage system charge state equalization method | |
| CN114006063B (en) | Balanced control method for lithium iron phosphate battery of pure electric vehicle | |
| CN114879053A (en) | Method for predicting service life of energy storage lithium iron phosphate battery |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |